Chromatic

A Cocoaheads presentation about the trials and tribulations of my first paid-for app

Transcript

1. Chromatic a crazy light painting physics thing Ray Hilton @rayh 1 Friday, 14 December 12
2. Motivation • 2yo daughter - There are lots of crap kid’s painting apps • Simplest possible UI - Ads, buttons, and dialogs distract • Play with OpenGL on iOS • Try and remember high-school vector maths • Experience the paid-app process 2 Friday, 14 December 12
3. 3 Friday, 14 December 12
4. 4 Friday, 14 December 12
5. 5 Friday, 14 December 12
6. 6 Friday, 14 December 12
7. 7 Friday, 14 December 12
8. Could I do better? • Put my money where my mouth is • Define the MVP • Short turnaround (1.5 months part time, ~80hours) • Use daughter as a tester • Shoot first, ask questions later 8 Friday, 14 December 12
9. Demo 9 Friday, 14 December 12
10. Promotion • Not indicative of suggested strategy, just my whimsical attempt • It’s been two months • $20 on Facebook Ads • $122 on Google Adwords • Twitter & Facebook posts 10 Friday, 14 December 12
11. $47.04 11 Friday, 14 December 12
12. ($94.96) 12 Friday, 14 December 12
13. Oh well 13 Friday, 14 December 12
14. OpenGL • I’m using OpenGL ES 1.0 • Previously used OpenGL in digital agency projects • Looked through many NeHe and Apple tutorials • Complex, procedural but very powerful • New terminology (Textures, Vertices, Fragments, etc) 14 Friday, 14 December 12
15. Metaballs! • Each particle has an intensity • Each particle’s intensity falloff is inversely proportional to r2 • At each pixel, add the intensities from each particle • ~4000 particles 15 Friday, 14 December 12
16. 0.5fps 16 Friday, 14 December 12
17. Cheat • Create radial falloff gradient in photoshop • Use glEnable(GL_POINT_SPRITE_OES); • Use glBlendFunc(GL_ONE, GL_ONE); • Constrain to ~1000 particle 17 Friday, 14 December 12
18. >30fps 18 Friday, 14 December 12
19. Yay! 19 Friday, 14 December 12
20. Ok, it wasn’t that simple... 20 Friday, 14 December 12
21. Performance • Use C-style structs, arrays, etc • Reuse allocated memory • Avoid doubles when floats will do • Use glVertexPointer(), et al • Use CADisplayLink 21 Friday, 14 December 12
22. Next • Try charging more/less • More creative promotion strategy • More interactions & effects • Look at using 3D metaballs for crazier effects • Ideally, use GLSL... 22 Friday, 14 December 12
23. GL Shader Language • OpenGL ES 2.0 has a programmable pipeline • C-style language that is executed on the GPU • Write vertex & fragment “shaders” • Reduces sync between the GPU and CPU 23 Friday, 14 December 12
24. Thanks 24 Friday, 14 December 12